The invention pertains to a lock which is used in particular as a rear lock in the trunk lid of a motor vehicle. In this lock, the cylinder core of the lock cylinder can be rotated by a properly fitting key out of a neutral position, which is determined by a pulse spring, into any one of three different working positions. After rotation in a pulse-wise manner into a first working position, called the "unsecured" position, the lock can be opened by the operation of a handle. In this position, an active connection between the lock and the handle is established. This does not apply to the second and third working positions, called the "secured" and the "safe-secured" or simply "safe" positions, respectively. In these cases, the handle is inoperative, for which reason the lock does not move when the handle is actuated. In the neutral position, a key can be inserted into the cylinder core and removed again; its pulse spring automatically returns the cylinder core to this neutral position from the unsecured or secured position. A key can also be inserted and removed in the safe position, in which the cylinder core remains after it has been rotated by the key.
The rotation of the cylinder core of the lock into the various working positions is reported to a central locking device, referred to in abbreviated form below as the "CL" device. The CL device acts on other locks on the motor vehicle, which are controlled in a corresponding manner. The locking mechanisms provided for these additional locks are rendered operative or inoperative by the CL device in the same way. But when the lock is in its safe position, the CL device cannot bring it back again into the unsecured position (in which the handle can be used to open the associated lock) when a key is used to actuate the cylinder core of any of the other locks.
When a key is used to rotate the cylinder core, a switch actuator is moved as well; as this actuator moves from the neutral position to the secured position or from the neutral position to the unsecured position, it actuates a microswitch. In each case, this microswitch initiates specific additional functions in the motor vehicle; for example, it can initiate the previously mentioned control function of the CL device or turn an electrical anti-theft warning system on or off. When the cylinder core is rotated beyond the secured position and into the safe position, the switch actuator moves to the other side of the microswitch, where, in the case of the known lock, it is held. Therefore, as already mentioned, the locking mechanism belonging to this lock remains blocked in the safe position, because the handle is inoperative. When, in the known lock, a key is used to rotate the cylinder core out of the safe position and back into the neutral position, so that the key can be removed again in the neutral position, the cylinder core passes through the secured position again on its return route, and the switch actuator actuates the microswitch again. As a result, the functions associated with the secured position are initiated yet again, such as, for example, the turning-on of the anti-theft warning system, the blocking of the locking mechanism, and the blocking of the CL device. In the case of the known lock, this can lead not only to inconvenient situations but also to dangerous ones.
A dangerous situation can result in the case of a vehicle with an array of locks on the doors and on the tailgate, which can be controlled from a central location by the CL device. Whereas the locks on the doors have three working positions (neutral position, secured position, an unsecured position), the lock for the tailgate can also be moved into the previously mentioned safe position; in the case being assumed here, this is the position in which it is supposed to remain. When a key is then used in one of the locks to change the locks on the doors into the unsecured position by way of the CL device, the lock on the tailgate remains in the safe position. When, finally, a key is used to turn the lock on the tailgate back into the neutral position (not to the unsecured position) and the key is pulled out, the switch actuator located at the tailgate passes over the microswitch, when initiates the cited functions for the secured position again. This means that the CL device is induced to return the locks of all the doors to the "secured" position. Now all the doors of the vehicle are closed, and any passengers who may be in the vehicle are trapped.
Another conceivable case, which is relatively harmless but still inconvenient, is present when the tailgate lock is moved back from the safe position to the neutral position while one of the doors is open. In this case, the anti-theft warning system is turned on and an alarm is triggered when the switch actuator moves across the microswitch. This leads to unnecessary noise.
The invention is based on the task of developing a reliable, compact lock which requires the fewest possible number of components and yet allows the cylinder core to be rotated between the neutral position and the three working positions cited above without the occurrence of any control problems involving the switch actuator carried along by the cylinder core.
Because, when the cylinder core is in the safe position, the control element is in a disconnection plane and thus automatically disengaged from the cylinder core, there is no need for any additional locking elements which would be required to disconnect the pulse spring from the cylinder core in the safe position. The pulse spring can always remain connected to the control element. It is also impossible for any contradictory control commands to be sent to the CL device; the reason for this is that, because the control element is situated in the disconnection plane, the switch actuator provided on the control element is a certain distance away from the microswitch and, when the actuator executes its return movement starting from the safe position, it passes by the microswitch without affecting it in any way. Although the control element with its switch actuator is automatically returned by the pulse spring to the normal position, which corresponds to the neutral position of the cylinder core, it nevertheless leaves the microswitch unactuated. When the cylinder core is returned by a properly fitting key from the safe position via the secured position to the neutral position, it no longer needs to return the control element, carrying the switch actuator, since the control element is already in its normal position, aligned with the core. In the neutral position of the cylinder core, a connection is established automatically again between the core and the control element, because the force of the spring acting on the control element moves it back into its connection plane. As the rotation continues and the cylinder core arrives in the unsecured position, the control element is able to move in the connection plane again and can use its switch actuator to actuate another microswitch, which then logically reverses the settings of the vehicle's electrical device thus, for example, deactivating the anti-theft warning system again and/or controlling the CL device.
An especially simple design of the lock according to the invention is obtained when the axial movement of the control element between the various planes is used to actuate one or more microswitches, which then can take over other functions in the motor vehicle. Thus, it is recommended that a third microswitch be inserted into the circuit of the two previously mentioned microswitches and that this third switch be actuated directly by the control element. The third microswitch can interrupt the entire electrical circuit when the control element moves out the connection plane into the disconnection plane or some other plane. This results in a very high level of security against forced entry in a vehicle equipped with this lock. It also means that a key in the cylinder core can turn the lock to the "safe" position or to a "garage" position.
Additional measures and advantages of the invention can be derived from the subclaims, from the following description, and from the drawings. The drawings present two different exemplary embodiments of the invention and also a simplified schematic diagram to help explain the special way in which the invention works: